On this post create three physical volume ( /dev/sda5 /dev/sda6 and /dev/sda7 ) each device have allocated 10 GB and combine into two different Volume groups (redhat, centos) then create two logical volumes (admin, user). Finally mount this volume to directory /admin and /user.

Assume that, I would like to create three device like /dev/sda5 /dev/sda6 and /dev/sda7 using fdisk command.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.